where n = 2, 3, 5, 7 and 9
Y
n
0
The nth harmonic frequency neutral admittance phasor.
I
n
0
The nth harmonic frequency zero-sequence current phasor.
V
n
0
The nth harmonic frequency zero-sequence voltage phasor.
B
o
n
The nth harmonic frequency susceptance,
Im
Y
n
0
( )
For fault direction determination, the fundamental frequency admittance and harmonic
susceptances are summed together in phasor format. The result is the sum admittance
phasor defined as below.
Y
Y
j
Y
Y
G
j B
osum
n
n
o
osum
=
+ ⋅
+
=
+ ⋅
=
∑
Re
Im
0
1
0
1
0
2
9
1
GUID-6660AD60-0694-4808-8146-A1F053DA5F7C V1 EN
(Equation 57)
The polarity of the polarizing quantity (residual voltage) can be changed
(rotated by 180 degrees) by setting the
Pol reversal
parameter to "True" or
by switching the polarity of the residual voltage measurement wires.
Fault direction determination
If a ground fault is detected by the GFC module, the fault direction is evaluated based on
the calculated sum admittance phasor
Y
osum
obtained from the Multi-frequency
admittance calculation module. To obtain dependable and secure fault direction
determination regardless of the fault type (transient, intermittent, restriking, permanent,
high or low ohmic), the fault direction is calculated using a special filtering algorithm,
Cumulative Phasor Summing (CPS) technique. This filtering method is advantageous
during transient, intermittent and restriking ground faults with dominantly non-sinusoidal
or transient content. It is equally valid during continuous (stable) ground faults.
The concept of CPS is illustrated in
. It is the result of adding values of the
measured sum admittance phasors together in phasor format in chronological order during
the fault. Using the discrete sum admittance phasors
Y
osum
in different time instants
(t
1
...t
5
), the corresponding accumulated sum admittance phasor
Y
osum
CPS
_
is calculated.
This phasor is used as directional phasor in determining the direction of the fault.
1MAC059074-MB A
Section 4
Protection functions
615 series ANSI
441
Technical Manual
Summary of Contents for Relion 615 series
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